In this specification, the term xe2x80x9cleadxe2x80x9d is used to mean xe2x80x9ca conductor by which one circuit element is electrically connected to another,xe2x80x9d not the metal xe2x80x9cleadxe2x80x9d expressed by the symbol Pb.
1. Field of the Invention
The present invention relates to an optical transmitter module, an optical receiver module, and an optical transceiver module that is constituted by combining the other two modules. In this specification, these three modules are generically referred to as optical communication modules.
2. Description of the Background Art
FIG. 19 is a partially cutaway perspective view showing the cross-sectional structure of a laser diode transmitter currently in use. A laser diode (LD) 10 and a monitor photodiode (M-PD) 15, which monitors the intensity of the light transmitted by the LD 10, are placed in the package. Optical signals transmitted by the LD 10 enter an optical fiber 61 through a lens 60. Such an optical communication module is called a pigtail-type module because of its outward appearance. As shown in FIG. 20, a pigtail-type module 100 connected with a circuit substrate provided with a driver IC 20 and a C-R element 25, requires the leads of the laser diode transmitter to be bent to solder them to the circuit substrate.
Recent developments in optical communication technology requir smaller, less costly, and mass-producible optical communication apparatuses. In the conventional structures shown in FIGS. 19 and 20, the LD is produced separately from the circuit substrate provided with the driver IC and other related devices. This production method has unsatisfactory limitations in miniaturization, cost reduction, and mass production. The structure causes the connection between the LD and the circuit substrate to be performed solely by hand soldering. This connection method prevents the improvement in the production efficiency.
The major factor causing the laser diode transmitter and the circuit substrate to be produced separately from each other is that there is no satisfactory means for electrically connecting the LD and the circuit substrate in a limited space at the time of the integration of the LD and the circuit substrate. The laser diode transmitter shown in FIG. 19 allows no more than four leads to be connected. On the other hand, at least 8 leads (sometimes 14 leads or more) are required when the leads for the IC for driving the LD are included.
Another reason for the separate production is that there is no satisfactory means for providing concurrently electrical insulation and thermal insulation at the time of the integration of the LD and the circuit substrate.
In order to solve the above-described problems, the principal object of the present invention is to offer an optical communication module that can be electrically connected in a limited space with the next-stage circuit substrate having a multitude of leads. Another object is to offer an optical communication module that can secure the electrical insulation and thermal insulation between the optoelectronic device, such as a light-emitting device and a light-receiving device, and the electric-circuit part and that has a property of high-speed response. Yet another object is to offer a particular method of connecting the optical communication module with the next-stage circuit substrate. This method eliminates the above-mentioned hand soldering, stabilizes the amount of the solder supplied to individual soldering places, effectively improves the quality of soldering, effectively reduces the cost, and facilitates mass production.
An optical communication module of the present invention has the following structure:
(a) A plurality of electroconductive media are provided. Each of the electroconductive media has a plurality of electroconductive pins, forms a multilayer structure with the other electroconductive medium or media, and protrudes from the main body of the optical communication module.
(b) At least one optoelectronic device selected from the group consisting of at least one light-emitting device and at least one light-receiving device is supported by one of the electroconductive media.
(c) An electric-circuit part being supported by one of the electroconductive media is connected to the optoelectronic device or each optoelectronic device.
(d) An optically coupling means supported by one of the electroconductive media is coupled optically with the optoelectronic device or each optoelectronic device.
The module may further have the structure that a connector portion is formed at the end portion of each of the electroconductive media to be connected to the next-stage circuit substrate.
The electroconductive media may be lead frames. The optically coupling means may be an optical fiber. A guiding structure that prevents the next-stage circuit substrate from shifting in a direction perpendicular to the protruding direction of the electroconductive media may be provided.
The module may have the following feature:
(a) The optically coupling means is an optical fiber inserted into a ferrule (hereinafter referred to as a ferruled optical fiber).
(b) The electroconductive media are two layers of lead frames.
(c) The connector portion is formed such that the next-stage circuit substrate can be securely inserted between the end portions of the lead frames.
The module may have a structure in which an Si platform supported by one of the electroconductive media is provided, and one end of a ferruled optical fiber is fixed on the Si platform together with an optoelectronic device.
The module may have the following feature:
(a) The light-emitting device is a laser diode (hereinafter referred to as an LD).
(b) The electric-circuit part connected to the LD is a driver IC.
The module may have the following feature:
(a) The light-receiving device is a photodiode (hereinafter referred to as a PD).
(b) The electric-circuit part connected to the PD is a signal amplifier.
The module may have the following feature:
(a) A signal-transmitting portion comprises at least one combination of an LD and a driver IC.
(b) A signal-receiving portion comprises at least one combination of a PD and a signal amplifier.
The module may have the following structure:
(a) An LD and an optical fiber coupled optically with the LD are supported by a part of a first lead frame.
(b) A driver IC is supported by a part of a second lead frame.
(c) A combination of the LD, the optical fiber coupled optically with the LD, and the driver IC forms a signal-transmitting portion.
(d) A PD and an optical fiber coupled optically with the PD are supported by the remaining part of the first lead frame.
(e) A signal amplifier is supported by the remaining part of the second lead frame.
(f) A combination of the PD, the optical fiber coupled optically with the PD, and the signal amplifier forms a signal-receiving portion.
(g) A resin-molding portion encloses the signal-transmitting portion and the signal-receiving portion for forming a package.
(h) A connector portion formed at the end portion of each lead frame protrudes from the package.
The module may have the following feature:
(a) At least one light-emitting device, at least one light-receiving device, or both are supported by a first electroconductive medium;
(b) At least one electric-circuit part is supported by a second electroconductive medium; and
(c) An electric insulator is sandwiched between the first and second electroconductive media.
The module may have the feature of having at least three layers of the electroconductive media. The module may have the feature of having at least two optoelectronic devices. The electroconductive media may be metal lead frames.
The module may have the following feature:
(a) The module further comprises at least one Si platform.
(b) At least one light-emitting device, at least one light-receiving device, or both are supported by a first electroconductive medium through the Si platforms.
(c) At least one electric-circuit part is supported directly by a second electroconductive medium.
(d) An electric insulator sandwiched between the first and second electroconductive media has a thermal insulation property.
The module may have the following feature:
(a) At least two light-emitting devices are incorporated into the module.
(b) The light-emitting devices are LDs.
(c) The electric-circuit parts connected to the LDs are driver ICs.
The module may have the following feature:
(a) At least two light-receiving devices are incorporated into the module.
(b) The light-receiving devices are PDs.
(c) The electric-circuit parts connected to the PDs are signal amplifiers.
A first electroconductive medium and a second electroconductive medium may protrude in a direction different from each other.
An optical communication module of the present invention has the following structure:
(a) A plurality of electroconductive media are provided. Each of the electroconductive media has a plurality of electroconductive pins, forms a multilayer structure with the other electroconductive medium or media, and protrudes from the main body of the module.
(b) A light-emitting device and a light-receiving device are supported by one of the electroconductive media.
(c) An electric-circuit part supported by one of the electroconductive media is connected to each of the light-emitting device and the light-receiving device.
(d) An optical wavelength demultiplexer is supported by one of the electroconductive media.
(e) An optical fiber supported by one of the electroconductive media is coupled optically with the light-emitting device and the light-receiving device through the optical wavelength demultiplexer.
(f) A connector portion is formed at the end portion of each of the electroconductive media to be connected to the next-stage circuit substrate.
The foregoing module equipped with an optical wavelength demultiplexer may have the following additional structure:
(a) An Si platform is supported by one of the electroconductive media.
(b) One end of the optical fiber is fixed on the Si platform together with the light-emitting device and the light-receiving device.
In the present invention, a method of connecting an optical communication module with the next-stage circuit substrate comprises the following steps:
(a) providing an optical communication module comprising:
(a1) a multiple layers of electroconductive media;
(a2) at least one optoelectronic device selected from the group consisting of at least one light-emitting device and at least one light-receiving device, the optoelectronic device or each optoelectronic device being supported by one of the electroconductive media;
(a3) an electric-circuit part connected to the optoelectronic device or each optoelectronic device, the optoelectronic device or each electric-circuit part being supported by one of the electroconductive media;
(a4) an optically coupling means coupled optically with the optoelectronic device or each optoelectronic device, the optoelectronic device or each optically coupling means being supported by one of the electroconductive media; and
(a5) a connector portion formed at the end portion of each of the electroconductive media;
(b) forming solder bumps at a connecting portion of the next-stage circuit substrate to be connected with the optical communication module;
(c) fitting the connecting portion of the next-stage circuit substrate between the connector portions of the optical communication module; and
(d) connecting the fitted portion by soldering accompanied by non-contact heating.
The soldering may be performed by reflow soldering. The solder bumps may be formed concurrently by the heat for soldering electrical components onto the next-stage circuit substrate. The testing of the optical communication module may be conducted by tentatively connecting it with a testing substrate before the step of fitting.
The connecting method may have the following additional steps:
(a) resin-molding the optical communication module so as to provide the structure of a package, with the end portions of the electroconductive media protruding from the package, before the step of fitting; and
(b) subsequently to the step of connecting, resin-encapsulating the exposed portions of the electroconductive media between the package and the next-stage circuit substrate.